1. Field of Invention
The present invention relates to a combustion phase detection method that uses a volume change rate and a pressure of a combustion chamber.
2. Description of Related Art
In an internal combustion engine, an abnormal combustion process, for example, knocking, can be generated by spontaneous combustion of an unburned mixture that a fire does not yet reach. Long continued knocking can damage components of the combustion chamber by an increment of heat load and pressure shock.
An important parameter that affects a knocking tendency of the internal combustion engine is ignition timing. If the fuel/air mixture in the combustion chamber is ignited too early, the knocking can be generated. Accordingly, after a knocking process is detected in the internal combustion engine, there is a method that retards ignition timing so as to prevent the knocking at a next combustion stroke.
Excessively retarded ignition is related to efficiency loss, and accordingly a knocking control apparatus is used to detect knocking during combustion in the internal combustion engine. This part of knocking control is knocking detection. Meanwhile, the ignition angle is adjusted during knocking control. Knocking control like this is published in an international patent application PCT/DE 91/00170. Other adjustment parameters such as fuel/air mixture, charging, compression ratio, an engine operating point, and so on can be varied so as to reduce knocking sensitivity of the internal combustion engine.
Also, knocking control is separately performed for each cylinder, and in addition to knocking detection, separately adjusting an ignition angle for each cylinder has been published. Since a structure difference of a cylinder, inequitable distribution of knocking sensors, and a related knocking signal of a cylinder generate differences of cylinders in knocking control, a separate knocking control for each cylinder is to be used to optimize efficiency thereof and simultaneously knocking sensitivity is deteriorated thereby.
If the phase detection portion, in which signals based on synchronization of ignition and knocking control are transferred, breaks down, a new demand condition is given to the knocking control that is separately performed for each cylinder. The knocking control is performed with maximum security and maximum accuracy so as to achieve maximum efficiency, due to possible damage of the internal combustion engine and stability of the combustion.
On this account, the necessity for the combustion phase control shows a steady growth to achieve stability of the combustion and noxious exhaust gas reduction.
Generally, the combustion phase control method includes calculating total heat release (referring to a total heat release of FIG. 1) by using the following Equation 1 and a pressure inside the combustion chamber, and detecting a combustion phase by using a specific point of the total heat release (for example, 50% of the total heat release, MFB 50: 0.5 value of axis y coordinate of FIG. 1).
                                          ⅆ            Q                                ⅆ            θ                          =                                            1                              γ                -                1                                      ⁢            V            ⁢                                          ⅆ                P                                            ⅆ                θ                                              +                                    γ                              γ                -                1                                      ⁢            P            ⁢                                          ⅆ                V                                            ⅆ                θ                                                                        Eq        .                                  ⁢        1            
However, since the above heat generation analysis method is based on a thermal dynamics rule and it is very complicated mathematically and has a large size of calculation load, it is effective in a case that it is analyzed at a theoretical side with sufficient time, but there is a drawback that it is difficult to apply it to the combustion of the engine that is performed in real time.
Also, in the combustion phase detection method that uses a 50% point of the heat generation (MFB 50), as shown in FIG. 2, there was a problem that a larger error is generated in detecting the combustion phase, in a case that an offset is formed in a sensor measure value by heat impact when the cylinder combustion pressure is measured, as shown in a square pattern mark coordinator of FIG. 3, compared to a normal circle mark coordinator.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.